Localization of the Major NF-κB-activating Site and the Sole TRAF3 Binding Site of LMP-1 Defines Two Distinct Signaling Motifs

This is the authors' abstract. We don't add key points for this paper.

The TRAF3 molecule interacts with the cytoplasmic carboxyl terminus (COOH terminus) of the Epstein-Barr virus-encoded oncogene LMP-1. NF-kappaB activation is a downstream signaling event of tumor necrosis factor receptor-associated factor (TRAF) molecules in other signaling systems (CD40 for example) and is an event caused by LMP-1 expression. One region capable of TRAF3 interaction in LMP-1 is the membrane-proximal 45 amino acids (188-242) of the COOH terminus. We show that this region contains the only site for binding of TRAF3 in the 200-amino acid COOH terminus of LMP-1. The site also binds TRAF2 and TRAF5, but not TRAF6. TRAF3 binds to critical residues localized between amino acids 196 and 212 (HHDDSLPHPQQATDDSG), including the PXQX(T/S) motif, that share limited identity to the CD40 receptor TRAF binding site (TAAPVQETL). Mutation of critical residues in the TRAF3 binding site of LMP-1 that prevents binding of TRAF2, TRAF3, and TRAF5 does not affect NF-kappaB-activating potential. Deletion mapping localized the major NF-kappaB activating region of LMP-1 to critical residues in the distal 4 amino acids of the COOH terminus (383-386). Therefore, TRAF3 binding and NF-kappaB activation occur through two separate motifs at opposite ends of the LMP-1 COOH-terminal sequence.